5 Rigor Mortis “Death Stiffness”Normal Muscle ContractionCalcium released from membranes inside cell causes muscle fibers cells to contractActive transport then removes calcium so muscle fibers can relaxThis requires oxygen and an energy supplyThe Rigidity of DeathStiffness occurs because skeletal muscles are locked in a flexed position and are unable to relax.Calcium leaks out of cell and muscle remains in a contracted positionNo active transport after deathStarts within 2 hours of deathBegins with Head (Face) and neckPeak Rigor, At 12 hours the body is at its most rigid stateAt about 15 hours muscle fibers break down and softenStiffness gradually disappears after 36 hoursRigor may remain for up to 48 hours

6 Rigor Mortis The body is at its most rigid state Just over 2 hoursObservationThe body is at its most rigid stateNo visible signs of rigorStiffness generally disappearsApprox. Time ScaleJust over 2 hoursLess than 2 hoursor more than 48 hours agoAfter 36 hours

9 Stomach and Intestinal ContentsIf undigested stomach contents are present, then death occurred 0 to 2 hours after last mealIf the stomach is empty but food is found in the small intestine, then death occurred at least 4-6 hours after last mealIf the small intestines is empty and wastes are found in large intestine, then death probably occurred 12 or more hours after last meal

10 Decomposition The rotting or break down of all tissues and organsBacteria and other microorganisms aid the decomposition process, just as they decompose plants and animals in the environment.Occurs in Predictable PatternCan be used to help determine Time of Death

11 Stages of DecompositionInitial DecayCorpse appears normal from the outside, but is starting to decompose from the actions of bacteria and autolysisPutrefecationOdor of decaying flesh is present and the corps e appears swollenBlack PutrefecationVery Strong odor. Parts of the flesh appear black. Gases escape and the corpse collapsesButyric FermentationCorpse is beginning to try out. Most of the flesh is goneDry DecayCorpse is almost dry. Further decay is very slow from lack of moisture

12 Timeline of Events during DecompositionWithin 2 days after death:Cell Autolysis begins following deathGreen and purplish staining occurs form blood decompositionThe skin takes on a marbled appearanceThe Face Becomes discoloredAfter 4 Days:The skin blistersThe abdomen swells with the gas carbon dioxide release by bacteria living in the intestinesWithin 6-10 Days:Corpse bloats with carbon dioxide, eventually gas causes the chest and abdominal cavities to burst and collapseFluids begin to leak from body openings as cell membranes ruptureEyeball and other tissues liquefyThe Skin sloughs off

13 Factors Affecting Rate of DecompositionTemperatureBodies decompose fastest within degrees Celsius (70-99 degrees Fahrenheit)Below this range rate decreases because cold temperatures slow the growth of bacteria and microorganismsAbove this range tends to dry out corpses and preserve themSeveral other factorsIllnessAgeWeightClothing or Lack of Clothing

14 Forensic Entomology Forensic entomologistCollects insect evidence from on, above, and below the bodyRecords environmental conditionsBecause life cycles are affected by fluctuations in the daily environmental conditions, insects cannot provide an exact time of death, only a close estimate.At crime lab some of the insects are raised under environmental conditions that mimic the environmental conditions at the crime scene to obtain most accurate approximation

15 Forensic EntomologyBlowflies are usually the first insects to arrive at a dead bodyUsually arrive within minutesBlowflies exhibit different life stagesEgg, larva (also known as instars), pupa, prepupa, adult

16 EggSoon after Death—blowfly eggs can be found in the moist, warm areas of a corpse< 8 hrs

23 Time of Death—InsectsThe insect life cycle provides scientists with a benchmark to estimate a time of deathInsect evidence cannot provide an exact time of death—fluctuating environmental conditionsInsect evidence provides a close estimate

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